The heart of a computer's long term memory is an assembly that is referred to as a magnetic disk drive. The magnetic disk drive includes a rotating magnetic disk, write and read heads that are suspended by a suspension arm adjacent to a surface of the rotating magnetic disk and an actuator that swings the suspension arm to place the read and write heads over selected circular tracks on the rotating disk. The read and write heads are directly located on a slider that has an air bearing surface (ABS). The suspension arm biases the slider toward the surface of the disk, and when the disk rotates, air adjacent to the disk moves along with the surface of the disk. The slider flies over the surface of the disk on a cushion of this moving air. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic transitions to and reading magnetic transitions from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
In order to increase the data density of such magnetic data recording systems, the track-width of the system can be reduced while the linear density of the system can be increased. However, the data density of current and future recording systems is fast approaching the point that is has become very difficult to maintain good data resolution. One of the problems experienced at such high data densities is erasure of data due to thermal energy. When the track-width of the system is very small, media should have smaller grains with higher coercivity to minimize the superparamagnetic effect. However, there is a limit to scaling media grain size and coercivity. One way to minimize the superparamagnetic erasure of magnetic hits is to define a large, thermally stable bit on the magnetic medium
Patterned magnetic recording media have been proposed to increase the data density in magnetic recording, data storage, such as hard disk drives. In bit patterned media (BPM), the magnetic material is patterned into small isolated blocks or islands such that there is a single magnetic domain in each island or “bit”. The single magnetic domains can be a single grain or can consist of a few strongly coupled grains that switch magnetic states in concert as a single magnetic volume. This is in contrast to conventional continuous media wherein a single “bit” may have multiple magnetic domains separated by domain walls. U.S. Pat. No. 5,820,769 is representative of various types of patterned media and their methods of fabrication. A description of magnetic recording systems with patterned media and their associated challenges is presented by R. L. White et al., “Patterned Media: A Viable Route to 50 Gbit/in2 and Up for Magnetic Recording?”, IEEE Transactions on Magnetics, Vol. 33, No 1. January 1997, 990-995.
Similarly, discrete track media (DTM) consists of patterned isolated tracks where the magnetic storage layer of the media is removed between tracks. DTM creates a hybrid situation relative to BPM, where media in the downtrack direction is similar to conventional continuous media, but has patterned tracks in the cross-track direction.
Patterned media with perpendicular magnetic anisotropy have the desirable property that the magnetic moments are oriented either into or out of plane, which represent the two possible magnetization states, it has been reported that these states are thermally stable and that the media show improved signal-to-noise ratio (SNR) compared to continuous (un-patterned) media.